Re: macbook problem.

Is in in NTFS format? If it is then OS X won't write to it, but WILL read from it. If you have the status bar enabled in Finder you will see an edit pencil with a bar through it (an icon) in the bottom right of the finder window, indicating that you cannot edit the contents of the drive.

You may need to format the drive to HFS+ or exFAT (FAT64) so your OS X can actually read and write to the drive; OR download and install a third party application e.g. NTFS-3G which adds a compatibility layer to support OS X (http://macntfs-3g.blogspot.com/);